1. Field of the Invention
The present invention relates to a camera having a vibration correction lens and a method for correcting image vibration, such that at least one portion of the vibration correction lens can move in a direction of the optical axis of the camera or in a direction orthogonal to the optical axis and, more particularly, to a camera having a movable lens suitable as the vibration correction lens to prevent image vibration on the imaging plane of the camera.
2. Description of the Related Art
Cameras have been made markedly more electronic in recent times, to include automatic exposure functions and autofocus functions, with a high degree of automation. However, in these types of automated cameras, one aspect of automation in which attempts have been insufficient is that of countermeasures against image vibration due to hand tremor and the like arising during hand-held photography.
Various vibration correction devices have been proposed to incorporate such countermeasures, particularly those countermeasures preventing image deflections arising from the tilting of the camera. These various vibration correction devices detect the vibrations or vibratory motions of the camera, and based on the result of this detection, image vibrations in the imaging plane are prevented.
Namely, a camera having an anti-vibration function, equipped with a prior art vibration correction device, detects the angular velocity or angular acceleration of the vibratory motion of the camera which is caused by hand tremor. According to these detected values, a suitable amount of correction of the image vibration in the imaging plane due to the hand tremor is calculated by a microcomputer, or some other calculating unit. Based on the result of this calculation, a vibration correction lens system arranged in the lens barrel and driven by a drive mechanism in either an up and down or right and left direction (a direction orthogonal to the optical axis), performs a correction of the photographic light path such that the image is brought to a standstill in the image plane.
A vibration detection unit used in the prior art camera is, for example, an angular velocity sensor, or an acceleration sensor using a piezoelectric element, which detects the force received when a physical body rotates, the so-called "Coriolis force". Moreover, in place of using a vibration correction lens system, the vertex angle of a variable vertex angle prism can be changed. Furthermore, a voice coil or an electric motor, is used, for example, as an actuator to drive the vibration correction lens system or the variable vertex angle prism.
In a camera having such an anti-vibration function, in the case in which the optical axes of the vibration correction lens and the other optical lens system of the camera coincide, the optical performance of the optical system is not degraded. However, in the case of performing a vibration correction, when the vibration correction lens moves and its optical axis is displaced from the optical axis of the other optical lens system, the optical performance is degraded from what it was when the optical axes coincided.
Thus, in a camera having an anti-vibration function, better photographs are obtained when photographed in a given position in which the optical axis of the correction lens and the optical axis of the other optical system coincide or in a vicinity of this given position.
However, in the abovementioned prior art cameras having an anti-vibration function, the problem is that in the case of photographing without performing vibration correction, the position in which the vibration correction lens is held is not necessarily the position in which the optical performance is the best, the position of best optical performance being the one where the optical axis of the vibration correction lens coincides with the optical axis of the other optical lens system. Photographs taken such that the vibration correction lens is at an arbitrary position other than the position of best optical performance are degraded in resolution and the like in comparison with photographs taken with the vibration correction lens being in the position of best optical performance.
Moreover, even in the case of photographing while performing correction of vibration, when the amount of vibration is small and the amount of drive of the vibration correction lens is small, it is possible to take photographs with a better resolution when the correction lens is in a position in which the displacement of the optical axes of the correction lens and of the other optical lens system is small.
Because of this, devices for driving and holding the vibration correction lens in the position of best optical performance have been considered, but because a mechanical lock, which maintains the vibration correction lens in a position such that the optical axes of the optical systems coincide, and the like are set up for this purpose, there are problems in that the size of the device is increased, and the variability of the positional accuracy becomes large.
In addition, in the case of performing vibration correction, when the vibration correction lens is driven, instances occur when the vibration correction lens reaches the end of its drive range. One problem is that, at this time, upon reaching the end of the drive range with the drive speed of the correction lens in a fast state, an impact occurs due to the mechanical collision of the vibration correction lens with the body of the camera, resulting in a new vibration of the camera, and mechanical breakdown of the correction lens drive system occurs.